When I bought a set of speakers for my classroom, I had assumed that I could pick up a cheap amplifier at RadioShack for $15 or so.

Apparently, that's no longer the case. (My template for judging what things should cost was set in the 1980s. Every December, I'm still somewhat shocked that Christmas trees don't cost $12 anymore.)

After some searching, I found this Kenwood stereo receiver at a second-hand shop for $40. To describe it as solid-state would be an understatement. You could knock a rhinoceros unconscious with this thing.